1. Field of the Invention
The present invention relates to a solid support for bacterial culture. More particularly the present invention relates to an improved device for carrying out microbiological assays and related procedures utilizing solid growth media.
2. Description of the Prior Art
Solid growth media for cultivating bacteria have been used in diagnostics for over 100 years. The various applications included identification of causative infectious agents, based on the appearances of discreet colonies on differential and selective media, containing, where applicable, reagents and color indicators facilitating biochemical characterization. Similarly, the susceptibility of an infecting agent to a variety of antibacterial agents could be assessed.
A reversal of procedure, namely the use of a bacterial strain susceptible to any such agent enables the detection of the presence of that agent in an unknown sample. Several tests based on this principle are currently used to detect antibacterials in milk, food or in other substances of interest.
Similarly, appropriate bacterial strains and media can be applied to the detection of growth promoting agents or of agents otherwise affecting the growth or the biosynthetic, metabolic or enzymatic activities of the bacterial test strain.
The classical format of such "solid-phase" microbiological or bacteriological assays is the Petri dish containing agar based growth medium. Agar-agar, which is the most commonly used solidfying agent can be replaced with silica or gelatin or other gelling substances. Alternatively, absorbent materials, such as bibulous cellulose in the form of filter paper or cardboard or any other absorbent can be cut as desired and impregnated with liquid growth medium. The solidified, as well as the impregnating, growth medium may take the shape of the Petri dish or any other shape required, to provide the desired solid base for the assay.
The main advantages of solid base bacteriological assays are simplicity and economy. The economy is further increased by increasing the number of tests per area of the test plate. A single Petri dish can be subdivided to provide for more than one test. However, interference between adjacent test areas is often observed if more than 4-6 samples are applied to one dish. This is a major limitation to the use of the classical format in large-scale screening.
A partial solution has been provided by redesigning the format so as to accommodate more samples per area unit. For example, the Petri dish can be replaced with a tray subdivided to resemble a diminutive ice-cube tray. The resulting compartments are physically separated and each can accommodate one sample. This format is used by Gist-Brocades in their screening test (Delvotest) for antibiotics in milk.